36yd lpvo zero pros and cons

[Sidneyious]

https://youtu.be/HFE-wj7sOs0

[Molon]

The 36 yard zero was originally nothing more than a field expedient distance (near zero) for obtaining a 300 yard far zero when using the M16A2 with its 20” barrel firing M855.





Pop quiz.

What is the most commonly missed target on the US Army 300 meter pop-up range, when using a 300 meter zero?

a.) 50 meter target
b.) 150 meter target
c.) 300 meter target
d.) None of the above



AR-15 Zeros and Trajectories


The 100 yard zero with a .223/5.56mm AR-15 carbine is a unique trajectory in that the bullet just “kisses” the line of sight at 100 yards and rides along it for approximately 10 yards before dropping back down below the line of sight. (Technically, the bullet does travel above the line of sight, but by only 0.010”; a fraction of the diameter of the bullet itself.)







For all other zeroing schemes, there are going to be two points were the bullet crosses the line of sight; the near-zero and the far-zero. For the near-zero, the bullet will cross the line of sight while traveling upward from the muzzle toward the apogee or “maximum ordinate,” its highest point of travel. For the far-zero, the bullet will cross the line of sight while traveling downward from the maximum ordinate.

Now, when assigning a name to a particular zeroing scheme, it would be helpful if that name gave descriptive information about that particular zero; that is, the name should give us information about the trajectory and how it is unique and differs from other trajectories.

As a point of reference, the Santose Improved Battlesight Zero is often referred to as a 50/200 yard zero, however this is incorrect. It is actually a 50 yard/200 meter zeroing scheme; and this is only with a very few particular combinations of bullet weight, barrel length/muzzle velocity and height of sights above the bore. As an example, a 20” barreled AR-15 A2 firing 62 grain M855 will not match the 50 yard/200 meter IBZ. Neither will a 16" barreled RECCE firing 77 grain MK262, nor a 14.5” barreled M4 carbine firing the 70 grain 5.56mm Optimized "Brown Tip" load. The same concept applies when people refer to a 50/225 yard zero. Only a very few specific combinations of bullet weight, barrel length/muzzle velocity and height of sights above the bore will match that description.

What this is all leading up to is this; except for a very few specific combinations of bullet weight, barrel length/muzzle velocity and height of sights above the bore, a 50 yard zero is a different zero than a 200 yard zero. For a 200 yard zero, we know that this trajectory will produce a far-zero in which the bullet will cross the line of sight at 200 yards in its downward travel from the maximum ordinate. (It is physically impossible to produce a 200 yard near-zero with any of the commonly available loads and barrels lengths used in .223/5.56mm AR-15s.) Other than for a very few specific combinations of bullet weight, barrel length/muzzle velocity and height of sights above the bore, the near-zero of the 200 yard zero will not be at 50 yards.

Conversely, a 50 yard zero tells us that this trajectory will have a near-zero in which the bullet crosses the line of sight at a distance of 50 yards in its upward travel to the maximum ordinate. For those who think that a zeroing scheme must be named after its far-zero, it is physically impossible to produce a far-zero of 50 yards with any of the commonly used loads and barrel lengths in .223/5.56mm AR-15s. The 50 yard zero can only be the near-zero.

Here are a couple of illustrations to aid in understanding some of the concepts described above. Lets start with the 100 yard zero as a reference point. As described above, with a 100 yard zero, the bullet’s trajectory just “kisses” the line of sight at 100 yards. Now, let’s increase the elevation setting of the sights/scope. As this is done, the near-zero can only move closer and closer to the muzzle. Concomitantly, the far-zero moves farther and farther away from the muzzle.







For the next illustration, we’ll start with the 100 yard zero again, only this time let’s decrease the elevation setting of the sights/scope. As this is done, the bullet’s trajectory can only fall away from the line of sight. The bullet will never cross the line of sight again; no zero at all.





Other than for a very few specific combinations of bullet weight, barrel length/muzzle velocity and height of sights above the bore, the far-zero of the 50 yard zero will not be at 200 yards; and for all practical purposes it matters not one bit. Whether the bullet crosses the line of sight for the second time (far-zero) at 189 yards, 200 yards, 215 yards or 225 yards will not make the slightest bit of difference in the practical application of the AR-15 as a defensive weapon. In each case we will be holding the same POA (beyond CQB distances) and know that we will be hitting within approximately 2 inches above or below that POA out to 200 yards (or farther depending upon barrel length and load.) You should have an idea what your actual far-zero is when using a 50 yard zero and confirm such at distance when possible, but again it’s most likely not going to be a 200 yard far-zero and again it does not need to be.

Choose your zeroing scheme based on the pertinent facts; not nonsense about “shooting through a cone.” When shooting at human targets, in the grand scheme of things there isn’t going to be any practical difference between a point of impact that has a negative deviation from the point of aim, (e.g. the bullet strikes 1.5” below the point of aim) and a point of impact that has an equal positive deviation from the point of aim (e.g. the bullet strikes 1.5” above the point of aim.) In other words, the absolute value of the point of impact from the point of aim (how far the point of impact deviates from the point of aim, regardless of whether it is a positive or negative deviation) is what we need to be concerned about. Therefore, one of the main points to consider when choosing a battle-sight-zero is this: What zeroing scheme produces the smallest absolute values for the deviations of the points of impact from the point of aim, over the distance that we reasonably expect to engage a human target in our intended usage?

The chart below illustrates the above concept. The chart compares the absolute values of the deviations of the points of impact from the point of aim (0.0 inches on the graph being the point of aim/line of sight) for a 50-yard-zero and a 100-yard-zero, using Hornady 5.56 TAP T2 ammunition.





As you can see in the graph above, from the muzzle (0 yards) to approximately 62 yards, the 50-yard-zero has a slight advantage over the 100-yard-zero. Between the distances of 62 yards and 165 yards, the 100-yard-zero has the advantage. From the distance of 165 yards out to the 250 yards shown in the graph, the 50-yard-zero has a distinct advantage over the 100-yard-zero.

Now, let’s add the 36 yard zero into the mix.





From the muzzle to approximately 42 yards, the 36 yard zero has a slight advantage over the 50 yard zero. From 50 yards out to approximately 235 yards, the 50 yard zero has a distinct advantage over the 36 yards zero. It isn’t until shooting past the distance of approximately 235 yards that the 36 yard zero regains any advantage over the 50 yard zero. Choose your zeroing scheme based on the pertinent facts.





Some reference material. Except where noted, all barrel lengths are 20 inches



Courtesy of zrxc77

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M855 25 yard zero





M855 25 meter zero





M855 36 yard vs 100 yard zero





M855



M855 and M193 25 meter zero



M855 and M193 50 yard zero from 16” barrel





M193 25 meter, 50 yard and 100 yard zeros from 16" barrel



100 yard zero



25 meter vs 50 yard zero, M855 from 16” barrel



25 meter vs 50 meter zero , M193 from 16" barrel



M855 300 meter zero



M855 200 meter vs 300 meter zeros





M855 36 yard vs 50 yard zeros

[mark5pt56]

my guess is 150, the boys who insisted on 25 zero's always seemed to be winged shots high as f at the 100 yard plates

[Stickman]

Not that it matters to anyone, but I use 36/300 for my Aimpoints. I have the ability to safely shoot rocks and dirt clods at unknown ranges, so without using calculus, I'm able to use different shooting positions and just shoot shit. Works good for this country boy.

Edit: somebody feel free to delete this as it has nothing to do with lvpos, apologies.

No need to delete it, I think the point stands on its own merit. As you point out, with what you are shooting, that zero method works for your needs. If MarkM was to use that same sighting in for shooting at 1000 yards, it would be wasted. However, if you were to use MarkMs method for your own needs, it would also be worthless. Without knowing what our objectives are, sometimes we are chasing an end goal we can never reach.

[Pappabear]

I zero all my gear at 100 yards and yet I can take my AR's to our pistol range and not miss whether it be 10 yards or 75 yards. The close targets are slants and a 6 pack of those MGM 8 inch MLS targets.

I think 2/3 inches in most combat situations is irrelevant. Long range precision DOPE is another story. I was shocked when I 100 yard zeroed my 10.5 LMT with 3 foot tall Unity mount and made consistent hits up close. I felt like I had everything against me but the gun went bang and the target popped.

Hence, we probably go overkill on worrying about 25/36/100 yard zeroes. Like said already, sight in and confirm via actually shooting. YMMV

PB

[C-grunt]

What is the reticle for your LPVO?

I had my Steiner P4Xi zeroed at 200 yards for the simple fact that was what the reticle called for. Was the BDC exact out at range? No. But they were on enough out to 500 yards that they would still score first round hits on IPSC steel.

For my red dots I like the 50 yard zero. Whether it's a little high or a little low at 200 yards doesnt really matter. Not that I can even realistically hold the difference at 200 yards with a red dot. I use it as a combat zero that gets me good COM hits from 0-300 yards. If it starts getting out towards the outer edge of the envelope, I just favor high on the target.

[C-grunt]

As to the original question... the 36 yards zero works. The 100 yard zero works. The 50 works.

Look at the graphs that Molon provided and choose the one you like most. They all have their pros and cons.

[Corse]

This video explains some benefits of different zeros.

https://www.youtube.com/watch?v=uAtU4lx2j_8

[MegademiC]

I zero all my guns 1" high at 100yds. I do this to extend no-hold range while eliminating hold-unders.

Then I get dope as far as the rifle will reliably hit.

What zero you choose doesnt really matter, learning holds does. Its going to be different based on load, optic hight, barrel length, etc

[NYH1]

I zero all our carbines with open sights or red dots at 50 yards which also zero's around 220 yards. All scopes get zeroed at 100 yards except for my 280 Rem. I zero that at 200 yards which is almost two inches high at 100 yards.

NYH1.